Note: Descriptions are shown in the official language in which they were submitted.
RCA 66, 718
1i :;7~6~
The present invention relates to a guided beam
type of flat display device wherein at least one and
preferably each of a plurality of electron beams is scanned
over a different area portion of an image screen. The
invention relates particularly to a scan deflection
structure for scanning each of the beams in one of its two
orthogonal scan directions within its area portion of the
10 Screen~
One structure whichXas been proposed for a large
area screen flat display device comprises a thin box-like
envelope with one of the~large sides thereof constituting
a faceplate on which a phosphor screen is disposed. Within
the en~elope are a plurality of spaced, parallel support
(against external atmospheric pressure) walls perpendicularly
disposed to and between the large sides of the envelope, the
walls forming a pluralit~ of parallel channels. Across one
end of the channels is a gun structure which directs at
.
least one electron beam along each of the channels. In
each of the channels is a beam guide which confines the
electron beam in the channel and guides the beam along the
length of the channel. The beam guide also includes means
for deflecting the electron beam out of the beam guide at
selected points along the beam guide. The beams in all of
- ;the channels are simultaneously deflected out oE the beam
,
guides toward the phosphor screen at each of the selected
points to achieve a line-by-line scanning of the phosphor
screen. This type of display device as disclosed by
3 - the prior art required as many beams as picture elements
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RCA 66.718
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1 desired for horizontal resolution in black-and-white operation,
and two or three times as many for color operation.
An electron display tube in accordance wikh the
invention also includes an evacuated envelope having a
substantially rectangular front wall and a phosphor screen
along the inner surface of the front wall. In the envelope
is means for generating a beam of electrons and directing
the beam in a first path generally parallel to and across
the phosphor screen. Along the first beam path is means for
selectively deflecting the beam out of the first path at
selected points along the first path into a second path
extending toward the phosphor screen so that the beam will
impinge on the phosphor screen. Along the second path -
of the beam is means for de~lecting the beam in a plane which
is transverse to the first path of the beam and thereby
cause~ the beam to scan at least a portion of the screen.
In the drawings:
FIGURE 1 is a perspective view of a guided beam
flat display device according to the present invention.
FIGURE 2 is a sectional view of a portion of the
display device taken along line 2-2 of FIGURE l.
FIGURE 3 is a sectional view of a portion of the
display device taken along line 3-3 of FIGURE 2.
Referring to FIGURE 1, a flat display device
including the scan deflection structure of the present
invention is generally designated as lO. The display device
lO comprises an evacuated envelope 12, typically of glass,
having a d1splay section 14 and an electronic gun section l6.
The display section 14 includes a rectangular front wall l8
30 ~ :
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RCA 66, 718
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1 which comprises the viewing screen, and a rectangular back
wall 20 in spaced parallel relation to the front wall 18.
The front wall 18 and back wall 20 are connected by side walls
22. The front wall 18 and back wall 20 are dimensioned to
correspond with the size o~ the viewing screen desired, e.g.
about 75 cm by 100cm, and are spaced apart typical]y about
2.5 to 7.5 cm.
As shown in FIGURE 2, a plurality of spaced,
substantially parallel, support walls 24, made of an
electrically insulating material such as glass~ are secured
between the front wall 18 and the back wall 20 and extend from
the gun section 16 to the opposite side wall of the envelope
12. The support walls 24 provide internal support for the
; evacuated envelope 12 against external atmospheric
` - 15 pressure and divide the display section 14 into a plurality
of channels 26. T~e edge of ~ach of the support walls 24
extending along the front wall 18 is tapered so as to
provide minimum area contact between the support walls 24
and the front wall 18.
On the inner surface of ~he front wall 18 is a
phosphor screen 28. For a black-and-white disp~ay, the phosphor
screen 28 is of any well known composition used in black-and-
white display devices. For a color display, the phosphor
screen 28 is pre~erably made up of alt~rnating strips of
conventional phosphor compositions which emit red, green and
blue light when excited by electrons. On the phosphor screen
28 is a film 30 of an electrically conauctive metal which is
,
transparent to electrons, such as aluminum. Fox a colox dis-
play, a shadow mask 32 extends across eaah of the channels
3Q ~6 adjacent to but spaced from the phosphor screen 28. The
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I shadow mask 32 is mounted on the support walls 24 and
extends thefull length of the channel 26. For a phosphor
screen 28 made up of alternating strips, the shadow mask 32
includes rows of elongated slits such as described in United
~States Patent No. 3,766,419, issued October 16, 1973 to R. L.
Barbin.
In each of the channels 26 adjacent the back wall
20 is an electron beam guide. The electron beam guide may be
of any construction which will guide one or more electron
beams alon~ a first path extending along the length of the
channel and allow deflection of the beam at spaced points
along the channel into a second path extending towards
the phosphor screen 28. As shown herein, the electron beam
guides are of the type disclosed in United States Patent
No. 4,103,204, issued 25 July 1978, to
T. Credelle.
The electron beam guide includes a first metal
ground plane 34 extending along the inner surface of the back
wall 20, and a second metal ~round plane 36 spaced from and
substantially parallel to the firs~ ground plane 34. The
first metal ground plane 34 has three U-shaped troughs 38
which face the second ground plane 36 and extend in
parallel relation along the entire length of the channel 26.
The first ground plane 34 may be made of a single sheet of a
conductive metal or may be a plurality of metal strips
ex~ending in parallel relation across the channel 26 ana
spaced longitudinally along the channel.
The second gro~nd plane 36 is of a sheet of an
electrically conductive metal and has three rows of spaced
'
RCA 66,718
7Z~Z0
1 holes 40 therethrough~with each row of the holes being over
a separate one of the troughs 38 in the first ground plane 34.
A plurality of wires 42 extend traversely across
the channel 26 between the first and second ground planes 34
5 and 36. The wires 42 are ~ansverse the longitudinal :'
dimension of the channel and are in spaced parallel relation
along the entire length of the channel 26. The wires are
positioned between the holes 40 in the second ground plane 36.
A focus plate 44 extends across each of the channels
10 26 adjacent to but spaced from the second ground plane 36, ~ -
and an acceleration plate 46 ex~ends across each of the
channels 26 adjacent to but spaced from the focus plate 44.
The focus plate 44 and the acceleration plate 46 are of an
electrically donductive metal and extend the full length of
the channel 26. The focus plate 44 and the acceleration
plate 46 each has three rows of holes 48 and 50 respectively
therethrough with the holes 48 and 50 being in alignment with
the holes 40 in the second ground plate ~6.
In each of the channels 26 are a pair of spaced,
suhstantially parallel deflection electrodes 52. The
deflection electrodes 52 extend between the acceleration
plate 46 and the shadow mask 32 along the entire length of :
the channel 26. Preferably, the deflection electrodes 52 are , :
on the surfaces of the support , walls 24 or side wall 22 ' :
25 which forms the sides of the particular channel 26. On the ,::
surface of each of the supporting walls 24 or side wall 22 ''
between the deflaction electrode 52 and the shadow ma~k 32 is
a lIne sampling electrode 54. . ,~ '
The gun section l6 of the envelope 12 is an
30 ,extension of the display section 14 and extends along one set -~
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1 of adjacent ends of the channels 26. The gun section 16 may
be of any shape capable of enclosing the particular gun
structure contained therein. The electron gun structure
may be of any well known construction suitable for
selectively directing at least one beam of electrons along
each of the channels 26. For example, the gun structure may
comprise a plurality of individual guns, one being mounted
at one end of each of the channels 26 for directing separate
beams of electrons along each of the channels. For a color
display device of the type shown in FIGURES 2 and 3, three
electron beams are required along each of the channels 26,
with each beam being directed along a separate one of the
troughs 38 in the first ground plane 34 of the beam guide.
However, for a black-and-white display device, only a single
beam is re~uired for each channel.
Another type of gun structure which can be used
includes a line cathode extending alQng the gun section 16,
across the ends of the channels 26, and adapted to selectively
direct inaividual beams of electrons along the channels. A
gun structure of this type is described in United States
Patent No. 2,858,464, issued October ?8, 1958 to W. L.
Roberts.
No matter what type of ~un structure is used in the
gun section 16, the gun structure should also include means
for modulating the electron beams~according to a video input
signal. As sh~wn in FIGURE 1, a terminal 56 extends through
a side wall 22 of the envelope 12. The terminal 56 includes
a plurality of terminal wires by which the gun structure and
other parts of the display within the envelope 12 can be
--electrically connected to suitable operating circuitry and
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1 power source outside of the envelope 12.
In the operation of the display device 10, the gun
structure in the gun section 16 generates and directs at
least one beam of electrons into each of the channels 26. For
a color display device preferably three beams of electrons are
directed into each of the channels 26. The electron beams
are directed between the ground p}anes 34 and 36 o~ the
beam guide with each beam being directed along a separate one
of the troughs 38 in the first ground plane 34. In the beam
guides, the ground plates 34 and 36 are at ground potentlal
and the wires 42 are at a positive potential. As described
in the aforementioned Uni~ed States Paten~ No.4,103,204,
this causes each of the electron beams to travel
in an undulating path along the wires 42 and between the
ground planes 34 and 36 along the entire length of the channel
26. The U-shapP of the troughs 38 causes electrostatic forces
to be applied to each of the electron beams as th~ beam passes
between the wires 42 and the first ground plane 34 to confine
the electrons of each beam between the sides of the troughs
so that each beam will flow along a separate one of the
troughs. Thus, each of the electron beams flows along a
first path along its respective channel 26 frQm the gun
section 16 to the slde wall 22 of the envelope 12 opposite
the gun section.
When the electron beams reach a selected point along
the guide, the electron beams are deflected out of the first
path into a second path extending toward the front wall 18
of the envelope 12. This can be achieved by switching the
potential applied to the wire 42 adjacent the side wall 22
to a negative potentiall or, if the first ground plane 34 i~
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RCA 66,7l8
~072~2~
1 in the form of a plurality of parallel strips, by switching
the potential applied to the strip adjacent the side wall 22
to a negative potential. The selected point of deElection out
of the guide is progressively moved along the guide toward
the electron gun end thereof to effect vertical scanning.
The deflected electron beams pass out of the beam
guide through adjacent holes 40 in the second ground plane 36.
The electron beams will then pass through the holes 48 in ~he
focus plate 44 and the holes 50 in the acceleration plate 46.
A potential positive with respect to the second ground plane
36 is applied to the focus plate 44 so as to focus the beams
as they pass through the holes 48~ and a potential also
positive with respect to the second ground 36,and preferably
the same potential às that on the metal film 30, is applied
to the acceleration plate 46 so as to accelerate the flow of
the beams as they pass through the holes 50. The electron
beams will flow toward the phosphor screen 28 by a positive
potential applied to the metal film 30 on the phosphor
screen 28.
As the electron beams flow along their second paths
from the acceleration plate 46 to the phosphor screen 28, the
electron beams pass between the deflection electrodes 52.
Initially, one of the deflection electrodes 52 in each of the
channels 26 is at a potential positive with respect to the
potential applied to the metal film 30 on the phosphor screen
28 and the other of the deflection electrodes is at a potential
negative with respect to the potential applied to the metal
film 30O This causes the second paths of the electron beams
to be deflected toward the deflection electrode which is at
30 - the positive potential. The potentials applied to the
_g_ ,.
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RCA 66,718
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1 deflection electrodes 52 are such that the second paths of the
electron beams are deflected sufficiently to cause the beams
to initially impinge on the phosphor screen 28 juxtaposed the
support wall 24 on which is the positively charged deflect-
ion electrode 52. The potentials applied to the deflectionelectrodes 52 are varied in conventional manner,by application
of appropriate deflection signals thereto,to effect a
horizontal scanning of the beam across a portion of the screen
equal to the width of a channel. By similarly deflecting the
beams in each of the channels across its respective channel,
a visual line will be created across the full width of the
phosphor screen 28 to achieve a complete horiz~ntal line scan
of the phosphor screen. The horizontal scanning of the
phosphor screen 28 is combined with the vertical scanning to
light up the entire screen. By modulating the beams at the
gun structure, a display can be achieved on the phosphor screen
28 which can be viewed through the front wall 18 of the display
device. ~ -
Each time the second paths of the beams are
deflected txansversely across the channels by the deflection
electrodes 52, at least one beam in each channel will impinge
on at least one if not both of the line sampling electrodes ;-
54. When a beam impinges on a line sampling electrode 54 an
electrical signal is generated in the electrode which can
be detected. This signal can be used to determine the position
of the beams so as to achieve proper alignment of the
corresponding beams in each~of the channels. This signal can
also be used to determine the beam current to insure uniform
brightness of the display across the screen. Thus, the line
sampling electrodes 54 can be used to detect the position
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RCA 66,718
1~372620
1 and/or the intensity of the current of the beams. This
information can be used to control ~he signals to the
deflection electrodes 52 to properly align all of the beams,
and/or control the signa~ to the gun structur to
achieve proper current levels and landing position at the
screen.
Although the display device 10 has been described
as having three beams directed along each of the channels 26
to achieve a color display, for a black-and~white display
. . .
only one beam of electrons need be directed into the beam
gu~de in each of the channels 26, and the shadow mask 32
would not be required. However, the display device would
operate in the same manner as previously described,with the
single beam in each of the channels 26 being deflected out
15 of its first path along the beam guide at a plurality of ~
points along the channel into second paths toward the phosphor ~ -
screen 28. As the beam passes between the deflection
electrodes 52,the beam would be deflected transversely across
the channel 26 to achieve line scans of the phosphor screen 28.
Thus, there is provided a flat display device in
which a plurality of electron beams are directed through ;
channels along first paths substantially parallel to the
phosphor screen on the front wall of the device. The beams
are deflected out of the first paths into second paths extend-
ing toward the phosphor screen at a plurality of spaced points
along the ~irst paths. As the beams pass along each of the
second paths.each of the beams i5 deflected across a plane
which traverses and is substantially perpendicular to ~he
first path of the beamvso that the beam sweeps hhe portion of
30 - the phosphor screen which extends transversely across the
RCA 66,718
1~7ZG20
l channel to provide a line scan of the phosphor screen.
By having each beam scan transversely across the
portion of the phosphor screen in each channel, the channel
being substantially wider than the diameter of the beam, the
numher of beams necessary to achieve a scanning of the entire
width of the display device is reduced. For example, for a
display device lO0 cm in width and having channels which are
2.5 cm in width, only 40 beams for black-and-white and 40
sets of three beams for color are necessary. This simplifies
the gun structure necessary for the display device. This
also simplifies the internal structure of the display device
by reducing the number of support walls and beam guides
required. Also, since the channels are much wider than the
diameter of the electron beams, the dimensional tolerances
lS of the widths of the beam guides are not as critical
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